Problem:
If you have already paid for a wild card certificate for a domain, it makes sense to use it wherever you can. In this example I am using an existing wildcard certificate used for the company website for an Exchange 2016 server.
Solution:
1. First you will need to download OpenSSL from here.
2. Next you will need to download the .CRT file from the certificate provider.
3. You will now need the original .KEY file (or certificate key hash) that was generated with the original certificate. (Someone in your company will have this!)
4. Run the command:
openssl pkcs12 -export -out C:\Temp\mycompanydomain.pfx -inkey C:\Temp\mycompanydomain.key -in C:\Temp\mycompanydomain.crt
5. The resulting .pfx file can then be imported into Windows using the certlm.msc personal certificates store.
